This invention pertains to the field of elevators, and in particular, to determining the absolute position and velocity of a moving elevator car.
To stop an elevator smoothly and level with a landing, the system must know when to initiate the stop, when to go into a leveling mode, and when to begin opening the elevator car doors. To perform these functions, it is necessary to know the exact position and velocity of the car at all times. A requirement has arisen to communicate with the car during the course of its travel and to transmit and receive commands and passenger data for automated vehicle applications. In the past, individual sensors have been developed for each requirement, resulting in the development of sensors without regard to operating frequency, commonality, and reliability.
Briefly stated, modulating digital data onto a carrier frequency and then amplitude modulating the result with a waveform of a different frequency permits measuring position and velocity of an elevator cab while transmitting digital data to the cab.
According to an embodiment of the invention, a method for determining range and velocity of an object compared to a station includes the steps of: (a) providing a reflector on the object; (b) modulating digital data at the station onto a first waveform using one of phase modulation and frequency modulation to produce a first output; (c) amplitude modulating the first output with a second waveform to produce a second output; (d) transmitting the second output from the station to the object, wherein a return signal is generated by a portion of the second output being reflected from the reflector; (e) receiving the return signal at the station and processing the return signal to obtain the range and the velocity of the object; and (f) processing the second output at the object to recover the digital data modulated onto the first waveform at the station.
According to an embodiment of the invention, a system for determining range and velocity of an object compared to a station includes means for providing a reflector on the object; means for modulating digital data at the station onto a first waveform using one of phase modulation and frequency modulation to produce a first output; means for amplitude modulating the first output with a second waveform to produce a second output; means for transmitting the second output from the station to the object, wherein a return signal is generated by a portion of the second output being reflected from the reflector; means for receiving the return signal at the station and processing the return signal to obtain the range and the velocity of the object; and means for processing the second output at the object to recover the digital data modulated onto the first waveform at the station.